1. Field of the Invention
The present invention relates to an optical waveguide device for a touch panel and a touch panel using the same.
2. Description of the Related Art
Touch panels are input devices for operating an apparatus by directly touching a display screen of a liquid crystal display device or the like with a finger, a purpose-built stylus or the like, and include a display which displays operation details and the like, and a detection means which detects the position (coordinates) of a portion of the display screen of the display touched with the finger or the like. Information about the touched position detected by the detection means is sent in the form of a signal to the apparatus, which in turn performs an operation and the like displayed on the touched position. Examples of the apparatus employing such a touch panel include ATMs in banking facilities, ticket vending machines in stations, portable game machines, and the like.
A detection means employing an optical waveguide is proposed as the detection means for detecting the finger touch position and the like on the above-mentioned touch panel (see, for example, US 2004/0201579 A1) Specifically, the touch panel includes optical waveguides provided around a periphery of a display screen of a rectangular display, and is configured to emit a multiplicity of light beams parallel to the display screen of the display from an optical waveguide provided on one side portion of the display screen toward the other side portion, and to cause the light beams to enter an optical waveguide provided on the other side portion. These optical waveguides cause the light beams to travel in a lattice on the display screen of the display. When a portion of the display screen of the display is touched with a finger in this state, some of the light beams are disrupted or blocked. Therefore, the light-receiving optical waveguide senses alight blocked portion, whereby the position of the portion touched with the finger is detected.
The light beams emitted from an optical waveguide directly into the air diverge radially. In this state, optical transmission efficiency is low. To enhance the optical transmission efficiency, an optical transmission device has been proposed in which a lens is placed at the front of an optical waveguide which emits light beams to thereby prevent the light beams from diverging, and another lens is similarly placed at the front of an optical waveguide which receives the light beams to thereby cause the light beams in a converged state to enter the optical waveguide (see, for example, JP-A-2003-4960). This optical transmission device is schematically shown in FIGS. 8(a) and 8(b) in which the optical transmission device includes an optical waveguide 10 and a lens device 20. The lens device 20 includes a mounting surface 21 for placing the optical waveguide 10 thereon, and a lens 22 formed to protrude from one edge portion of the mounting surface 21. The optical waveguide 10 is bonded to the mounting surface 21 of the lens device 20 with an adhesive 50 and is positioned so that light beams pass through the lens 22. The refraction through the lens 22 is used to prevent the divergence of light beams (indicated by the arrow shown in FIG. 8(b)) emitted from the optical waveguide 10 and to converge light beams incident upon a light-receiving optical waveguide 10 in a manner described above.
In the above-mentioned optical transmission device, however, the light beams do not appropriately pass through the lens 22 so that the optical transmission efficiency is not sufficiently enhanced unless precise alignment is performed between the optical waveguide 10 and the lens 22. Additionally, the precise alignment requires accuracy and is hence difficult. It is labor- and time-consuming to achieve the precise alignment.
Further, it is necessary to bond the optical waveguide 10 and the lens device 20 to each other with the adhesive 50. During the bonding, the adhesive 50 sometimes squeezes out of a peripheral edge of the optical waveguide 10 to deface a peripheral portion of the optical waveguide 10, thereby causing a hindrance to optical transmission.